Yes, they're clappy and they know it

Alex Preston's new novel takes a swing at the evangelical Alpha male. He tells Danuta Kean what led him to it

Alex Preston attended an Alpha Course while working in the City. 'These things are riven with hypocrisy,' he says

A few years ago, in the pub after work, I laughingly told my then colleagues that I had once been a member of a church affiliated to the notorious Nine O' Clock Service, where people spoke in tongues and danced down the aisles. The silence, coupled with looks of shocked embarrassment, said it all.

If I could have given them a copy of Alex Preston's second novel The Revelations, they may have congratulated me for getting out with my sense of humour intact. The novel follows Preston's 2010 debut This Bleeding City, and like that book deals with the emotions and moral compromises of a group of young people with ties to high finance.

However, unlike in This Bleeding City, this group are evangelical Christians, leaders of The Course, which is loosely based on the Church of England's Alpha Course. In the novel, The Course uses weekly study and intensive weekend workshops to introduce wealthy young Londoners to a happy-clappy version of Christianity. Once committed, they find the organisation's growth is paramount and the consequences of the pastoral indifference that this generates are devastating.

The Revelations was inspired by a conversation its author had in 2005. "A friend was told by her boyfriend that if she didn't attend the Alpha Course he would stop sleeping with her," Preston relates. Amused by my incredulity, he adds: "These things are riven with hypocrisy."

They are also full of possibilities for talented writers such as Preston. As well as referring to plot developments and religious insights, The Revelations is the name of the Christian rock band formed by the four main characters. As the book opens, the band members prepare to lead their first Course. Semi-homeless Mouse is obsessed with Lee, a suppressed free spirit whose enforced denial of her sexuality manifests as self-destruction; corporate lawyer Marcus, whose smug pretence masks deep doubts about God and his marriage; and sanctimonious Abby, Marcus's wife and the band's vocalist. All of them are under pressure from Course founder David Nightingale to convert a disparate group of seekers, the kind of souls that wash up on church steps in London looking for companionship as much as meaning.

They will not find either with Nightingale. An evangelising celebrity vicar, he ruthlessly exploits each character's vulnerability. I tell Preston I have bad memories of his type, and he reveals that he had one man firmly in his sights when creating Nightingale: Tony Blair. "It was the sense that there was all this youthful energy and enthusiasm [about him] and in the end he is just like an old whore doing the rounds. It is very much money, money, money." He rubs his thumb and forefinger together with a grimace.

Love of money is the sin that slides in behind the Course's vehement opposition to sex outside marriage. This obsession, which blinds Nightingale to more dangerous issues, was something Preston saw in his mid-twenties at an Alpha Course. "What I found particularly weird was the way they were so punitive on sex and relatively liberal on so much else." It was one reason he rejected the teachings.

In an excruciating scene, Nightingale takes Lee aside to warn her that her promiscuity risks her ejection from the group. The character is based on a young woman Preston knew on the Alpha Course, and he remains angry that she was left to flounder. "It was clear from a five-minute conversation with her that she was tortured [about sex] and yet nobody had thought to speak to her about it, beyond making clear that if she had sex before marriage she would go to Hell."

I mention the amount of sex in the book, and the mood changes. "I tweeted yesterday that I am unable to write sex scenes before lunch," he giggles. The book's scenes of unsatisfactory sex graphically illustrate failures in intimacy; even marital sex feels grubby. The characters seek relief in uninhibited worship instead, which emphasises their isolation and the futility of their religious experience.

But money, not sex, is the dark heart of The Revelations. It is something that the 33-year-old Oxford graduate knows all about. Until five years ago he was trading credit derivatives. Now, sitting in an office at the University of London where Preston is completing a PhD in English, I find it hard to reconcile the image of an investment banker with the man seated before me. The Armani suit has given way to the academic chic of jeans and cardigan.

Having jettisoned banking for academia, he regards the relationship between Church and City with distaste. "There are a lot of evangelical Christians in the City," he observes. "After attending Alpha, when I walked around the City I would see a lot of the people I had seen the night before. They were all working for hedge funds." He accepts that some donated much of their large salaries, but he is perplexed at their certainty about salvation: "There seems to me an absolutely fundamental friction between a Christianity that teaches poverty and abstinence, and people earning £5m a year."

Faith, for Preston, involves doubt. "Talk about the comfort of faith," he says with a bitter laugh. "I find it profoundly uncomforting because it is a struggle." I say that I am a "probable atheist". He laughs, "I like that." Yet he allows himself no such protection from what he describes as his own relentless "negative capability" to entertain uncertainty.

I am not convinced that his uncertain principles are so discomforting. Doubt is fertile ground for Preston, and when he says he left the end of The Revelations deliberately ambiguous, I see a flash of satisfaction that he has led readers along the same road.

Danuta Kean is books editor of Mslexia

The Revelations, By Alex Preston (Faber £12.99)

"You must fight against it. The Course will be there for you when you come out the other side of this phase you're going through. But if you backslide too far, if you let the Devil come too close to you, it may be that you are too distant for even the Course to reach you. If you become a slut, Lee, I might have to ask you to leave. For the good of the Course."